The PMS-1515D Pressure Chamber Instrument is a new release. It is similar to the PMS-615D model however it has a maximum operating pressure of 100 bar (10 MPa). The PMS-1515D is a highly portable pressure chamber for growers making routine water measurements and irrigation scheduling. It can also be used in scientific research and for pressure volume curves. The digital read-out offers features such as backlighting and multiple pressure scales (Bar, MPa and PSI). Standard sealing option is a ¼ inch Compression Gland Gasket and Insert which is ideal for most woody plants. Other sealing options for bladed grass or other semi-round sizes are available.
Model 1515D Pressure Chamber Instrument is a new release with changes that most users will appreciate. It is a 100 bar digital instrument fully enclosed in a sealed case with an easily removable tank. It is similar to our Model 615 except higher pressure and digital readout. The Control Valve and internal piping have been upgraded to now allow direct connection to Nitrogen Cylinders with 207 Bar/3000 PSI pressure. The instrument is fitted with a 100 Bar Digital Gauge that offers features such as backlighting and multiple pressure scales such as (Bar, MPa and PSI).
Instrument comes fitted with our most popular sealing gasket size – 1/4 inch Compression Gland Gasket and Insert. This gasket will seal a sample that is 1/4 inch in diameter down to a completely closed position. If you need other sealing options such as bladed grass or other semi-round sizes check our other options.
This is an excellent choice for research due to the large range of operating pressure. It is good for work on high stress level plants, pressure volume curves but can also be used for routine water measurements for crop plants.
The instrument has a bail-spring handle for carrying and comes complete with a shoulder strap to lighten the load in the field. It has 5 tie-down rings for mounting to ATV or other transportation. The instrument comes complete with light weight aluminum nitrogen cylinder (20 cubic foot) that is secured with 2 inch heavy duty velcro straps and can be quickly replaced with a full cylinder.
|Maximum Operating Pressure:||100 bar|
|Chamber Construction:||Solid Stock Stainless Steel|
Bar – PSI Scale
|Size (L x W x H):||56 × 38 × 26 centimeters|
|Gauge:||2.5” Diameter Gauge
1/2 of 1% accuracy
100 bar (10 Mpa) range
Principle of Operation
The pressure chamber can be thought of as measuring the “blood pressure” of the plant — except that for plants it is water rather than blood, and the water is not pumped by a heart using pressure, but rather pulled with a suction force as water evaporates from the leaves. Water within the plant mainly moves through very small inter-connected cells, collectively called xylem, which are essentially a network of pipes carrying water from the roots to the leaves. The water in the xylem is under tension. As the soil dries or humidity, wind or heat load increases, it becomes increasingly difficult for the roots to keep pace with evaporation from the leaves. This causes the tension to increase. Under these conditions you could say that the plant begins to experience “high blood pressure.”
Since tension is measured, negative values are typically reported. An easy way to remember this is to think of water stress as a “deficit.” The more the stress the more the plant is experiencing a deficit of water. The scientific name given to this deficit is the “water potential” of the plant. The actual physics of how the water moves from the leaf is more complex than just “squeezing” water out of a leaf, or just bringing water back to where it was when the leaf was cut. However, in practice, the only important factor is for the operator to recognize when water just begins to appear at the cut end of the petiole.
The Plant Moisture Stress (PMS) reading at any given time reflects the plant’s interaction with the water supply and the demand for water placed upon the plant by its environment. Since these factors are almost always changing, PMS is nearly always changing. The time of measurement therefore requires careful consideration — PMS is most at midday and least just before sunrise. Pre-sunrise PMS values will usually reflect average soil moisture tension, if the soil is uniformly irrigated. Midday PMS values reflect the tension experienced by the plant as it pulls water from the soil to satisfy the water demand of the atmosphere.
Van Leeuwen, C., Tregoat, O., Chone, X., Bois, B., Pernet, D., & Gaudillere, J. P. (2009). Vine Water Status is a Key Factor in Grape Ripening and Vintage Quality for Red Bordeaux Wine. How can it be assessed for vineyard management purposes? Journal of International Science Vigne Vin, 121-134. PDF
Van Leeuwen, C., Tregoat, O., Chone, X., Gaudillere, J. P., & Pernet, D. (2008). Different environmental conditions, different results: the role of controlled environmental stress on grape quality potential and the way to monitor it. Proceedings of the 13th Australian Wine Industry Technical Conference, 39-46. PDF